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LTE System OverviewLZU 108 7020 R3DChapter 3: Radio Interface

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Text 24 ptBullets level 2-520 pt Ericsson AB 2010. Figure 3 -Radio Interface*

Objectives of Chapter 3 - Radio InterfaceOn completion of this chapter the students will be able to: Describe the Radio Interface principlesList the radio interface protocolsDescribe the radio interface techniques used in uplink and downlinkDescribe the channel structure of the radio interfaceExplain the OFDM principle and benefitsDescribe the basic principle of MIMO


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Evolved UTRAN (EUTRAN)S1-UX2EUTRANeNodeBeNodeBUELTE UuS1-CeNodeB Responsibilities: Cell control and MME pool support Mobility control Control and User Plane security Shared Channel handling Segmentation/Concatenation HARQ Scheduling Multiplexing and Mapping Physical layer functionality Measurements and reporting


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Radio interface structureSegmentation, ARQCipheringHeader Compr.Hybrid ARQHybrid ARQMAC multiplexingAntenna and resrouce mappingCoding + RM Data modulation Antenna and resource mapping Coding Modulation Antenna and resource assignmentModulation schemeMAC schedulerRetransmission controlPriority handling, payload selectionPayload selectionRLC #iPHYPDCP #iUser #iUser #jMAC Concatenation, ARQDecipheringHeader Compr.Hybrid ARQHybrid ARQMAC demultiplexingAntenna and resrouce mappingCoding + RM Data modulation Antenna and resource demapping Decoding Demodulation RLCPHYPDCPMACeNodeBUERedundancy versionIP packetIP packetEPS bearersE-UTRA Radio BearersLogical ChannelsTransport ChannelsPhysical Channels


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ARQ vs HARQeNodeB


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Polling ARQ System (RLC)


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Hybrid ARQ with Soft CombiningFrame


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LTE Air Interface IntroductioneNodeBLTE UEsRRC_CONNECTED

RRC_CONNECTED


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Downlink: OFDMOrthogonal Frequency Division MultiplexingBenefits+ Frequency diversity + Robust against ISI + Easy to implement + Flexible BW + Suitable for MIMO + Classic technology (WLAN, ADSL etc)DrawbacksSensitive to doppler and freq errorsHigh PAPR (not suitable for uplink)Overhead Orthogonal: all other subcarriers zero at sampling point Sub carrier spacing 15 kHz (MBMS also 7.5 kHz) Delay spread C1layer)In practice, MIMO may be worse due toInter stream cross-talk => lowers MIMO SINR:sSINR imbalance

SINR: N+ISINR: /2Power: P/2N+ISINR: /2Power: P/2N+ISingle layerTwo layersCapacity (bps)/2/2C1layerC2layersSINRHigh SINR => greater chance multiple layers is better!


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Example of Spatial Multiplexing -DL SU-MIMO (SDM)RBSLayer 1Layer 2Layer 2


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Example of Spatial Multiplexing -DL SU-MIMO (SDM)RBSLayer 1Layer 2Layer 2


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LTE DL Physical Resources


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DL Physical ResourcefrequencytimeOne slot (0,5 msec) One subframe (1 msec) Modulation symbol ( 16.7 s)Resource Block (12 subcarriers)


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Time-domain Structure FDDNormal CP, 7 OFDM symbols per slotTCPTu 66.7 s#0#1#9One OFDM symbolOne slot (0.5 ms) = 7 OFDM symbolsOne subframe (1 ms) = two slotsOne radio frame (10 ms) = 10 subframes = 20 slots#2#3#4#5#6#7#8


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LTE ChannelsUL-SCHPCHDL-SCHPCCHLogical Channels type of information (traffic/control)Transport Channels how and with what characteristics (common/shared)DownlinkUplinkPDSCHPhysical Channels bits, symbols, modulation, radio frames etcMTCHMCCHBCCHDTCHDCCHDTCHDCCHCCCHPRACHRACHCCCHMCHBCHPUSCHPBCHPCFICHPUCCH-CQI -ACK/NACK -Sched req.-Sched TF DL -Sched grant UL -Pwr Ctrl cmd -HARQ infoMIB SIBPMCHPHICHPDCCHACK/NACKPDCCH infoMapped onto Downlink physical resourcesMapped onto Uplink physical resources


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Cell-specific Reference SignalsCell-specific reference signalsSequence is a product of1 of 3 orthogonal sequences1 of 168 pseudo-random sequences3168=504 different sequences 504 different cell identities

Used for coherent demodulation in the UEchannel-quality measurements for schedulingmeasurements for mobilityDownlink reference symbolOne slot (0.5 ms)TimeFrequency


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Cell-specific Reference Signals- multiple antennasOne reference signal per antenna port1, 2, or 4 antenna ports supportedspecified per antenna port, reference signals are not pre-coded

Different time/frequency resources used for different antenna portsNothing transmitted on other antennas when reference symbol transmitted on one antenna

Higher density in time for antenna 1, 2 than antenna 3, 4


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UL Channel-sounding Reference Signal


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RBS 6000 Family


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RBS 6000 Hardware Architecture


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RBS 6000 RU and DU VariantsGSMDUG+WCDMADUW+LTEDUL+RUSRUWRULMultistandard Support: GSM, WCDMA and LTE(two simultaneously)

+++RUG


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Radio Unit LTE Configurations

Configuration

No of RUs

Output Power (W)

3 X 20

3

60

3 X 20 MIMO

6

60 + 60

6 X 20

6

60

6 X 20 MIMO

12

60 + 60

3 X 20 | 3 X 20 (Dual Band)

3 | 3

60 | 60

3 X 20 | 3 X 20 MIMO (Dual Band)

6 | 6

60 + 60 | 60 + 60


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Digital Unit for LTE (DUL)Prepared for high peak rates2x2 MIMO64QAM DL & ULPrepared for the futureSupports for LTE System Architecture EvolutionSupports for multiple digital units & redundancyMultistandard readyMain unitCapacity*Up to 1000 usersUp to 173 Mbps throughput DLUp to 56 Mbps throughput ULIP transmission capabilityAll IP architecture with full non-blocking connectivity100/1000BASE-TSFP slot for 1000BASE-X

* Figures quoted based on Hardware


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RBS 6000 Multistandard NodeGSM 3x4 900LTE 3x20MHz 2600GSM 3x4 1800WCDMA 3x4 2100RBS 6201 Example


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RBS 6601 Main remoteRBS 6601 Main Unit: - One DUW (shown here) or 2 DUG/DUL Supplies -48 VDC to DUs Climate Control SystemRRUW: WCDMA Only - 20/40/60 W Output Power 4 Carriers

RRUS: - Multistandard support (two simultaneously) 20/40/60 W Output Power 4 Carriers (20 MHz for LTE)

Maximum of 12 connected to Main Unit for WCDMA


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UEs and Base Stations selectioneNodeBLTE UEstimefrequencyf=15 kHz1 ms180 kHzUE #2UE #1UE #3 Each UE uses a separate variable bandwith carriernx180kHz1 ms180 kHzRRC_CONNECTED

RRC_CONNECTED

Radio Interface UuEricsson AB 2010 Radio Interface In a conventional ARQ scheme, received data blocks that cannot be correctly decoded are discarded and retransmitted data blocks are separately decoded, In case of hybrid ARQ with soft combining, received data blocks that cannot be correctly decoded are not discarded. Instead the corresponding received signal is buffered and soft combined with later received retransmissions of the same set of information bits. Decoding is then applied to the combined signal.The use of hybrid ARQ with soft combining increases the effective received Eb/Io for each retransmission and thus increases the probability for correct decoding of retransmissions, compared to conventional ARQ.

Ericsson AB 2010 Radio Interface In a conventional ARQ scheme, received data blocks that cannot be correctly decoded are discarded and retransmitted data blocks are separately decoded, In case of hybrid ARQ with soft combining, received data blocks that cannot be correctly decoded are not discarded. Instead the corresponding received signal is buffered and soft combined with later received retransmissions of the same set of information bits. Decoding is then applied to the combined signal.The use of hybrid ARQ with soft combining increases the effective received Eb/Io for each retransmission and thus increases the probability for correct decoding of retransmissions, compared to conventional ARQ.

Ericsson AB 2010 Radio Interface Ericsson AB 2010 Radio Interface RBS 6102 is the large outdoor macro RBS providing a complete radio site including transport equipment, site power, 4U transport equipment and battery backup. The cabinet can house up to two radio shelves, two battery strings, thus designed for high capacity demands.

RBS 6101 is the small outdoor macro RBS. The cabinet can house one radio shelf and has space for one radio shelf, power, transport. The RBS 6101 can also be used as a site support cabinet when Main Remote is used. RBS 6101 can fit high capacity multistandard MR with power and battery back up to the entire MR RBS.

RBS 6201 is an indoor cabinet that can house 2 radio shelves as well as the transport equipment and site power supply needed for an entire RBS site. Thus this is a complete site, for high capacity demands integrated into one cabinet. The cabinet is containing two radio shelves that provides flexible radio capacity.

RBS 6601 is a very small indoor main unit that can be inserted into standard 19 racks already deployed at the site. RRU Radio Remote Units are the naming of the radio head and is designed to be mounted near the antenna to minimize the feeder loss, which gives drastically reduced site power consumption. The baseband controlling the RRU can be deployed either in macro enclosures (E.G RBS 6101, 6301) or in the 19 RBS 6601.

RBS 6301 can be used as a low capacity macro, a very compact high capacity main unit for single standard or multi standard main-remote sites or as a micro.

Ericsson AB 2010 Radio Interface Ericsson AB 2010 Radio Interface Ericsson AB 2010 Radio Interface High capacity - LTEFinally, the same shelf can be equipped with LTE radio units, each with 20 MHz bandwidth and 60 W output per unit. Maximum capacity is thus 3x20 MHz with 120W per sector.

Cabinet flexibilityBased on the high capacity per radio shelf, or even half a radio shelf, the next slides will look at the flexibility that can be achieved by combining radio shelves in a base stations. The example used is the RBS6102, the large outdoor base station.

Ericsson AB 2010 Radio Interface DUL is HW prepared for2x2 MIMO support64 QAM DL & UL supportEnables peak rates up to 173 Mbps DL and 56 Mbps UL

Support for LTE System Architecture Evolution (eUTRAN) supporting the S1 interface (towards core network) and eNodeB functionality over the X2 interface (between base station controllers)

All IP architecture, with fully non-blocking connectivity and routing

Flexible solutions including daisychaining , redundancy to meet different operator deployments

Support for MultistandardThe DUL is designed to work with RUS running in mixed mode (two standards simultaneously)

Main UnitThe interface of the DUL towards radio units can either be used for Macro (electrical i/f) or RRU (optical i/f). The interface selection is made in the connector in the cable.Ericsson AB 2010 Radio Interface

Again here the RBS6000 acts as a multi standard RBS

Ericsson AB 2010 Radio Interface Ericsson AB 2010

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